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1. Field of the Invention
The Invention begins with the method according to the features given in the preamble of claim 1. Such a method is known from the German printed patent document DE-196084 78 A1. The known tire pressure monitoring system provides a pressure sensor at each wheel of a vehicle, an electronic evaluation circuit connected to the pressure sensor, a transmitter, a transmitter antenna and a battery wherein the battery supplies current to an electronic circuit (designated in the following as wheel electronics) furnished at the wheel. Receiver antennas are furnished at the body of the vehicle neighboring to the wheels, wherein the receiver antennas are connected to a central receiver and evaluation circuit (designated in the following as central evaluation electronics) through cables.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
The unequivocal coordination of the transmitter to the position of its wheel at the vehicle is a problem posed in connection with such tire pressure monitoring systems. The transmitters generate for this purpose a signal subdivided in four sections, comprising a preamble, an identifier, a measurement signal and a postamble. The central evaluation electronics can recognize by way of the identifier (identification signal), where the emitting wheel is disposed at the vehicle. However it is a precondition for this that the identification signal and the wheel positions have been previously unequivocally coordinated and that this coordination was stored in the central evaluation electronics. The German printed patent document DE 19608478 A1 teaches a possibility, how this coordination can be automatically determined from the signals emitted from the wheel electronics after the first time mounting of wheels at a vehicle or after a wheel change. For this purpose a statistic evaluation of the signal intensities is performed: in fact each receiver antenna receives signals from all transmitting wheels of the vehicle, however one starts with the assumption that the signals from the wheel disposed closest to the respective receiver antenna are received with the largest intensity on a statistical average.
A similar coordination method is known from the German printed patent document DE 19608479 A1.
The conventional coordination methods are associated with the disadvantage that they cause substantial costs of the tire pressure monitoring system, because a separate receiver antenna is furnished for each wheel, which receiver antenna is to be connected to the central receiving and evaluation circuit in the vehicle with an antenna cable.
It is an object of the present invention to furnish a possibility to accomplish the automaic coordination of the identification signals emitted by the wheel electronics to certain wheel positions with low expenditures.